It is known that abradable sealing joints may be made of compound metallic material (colmated ho neycomb, felt, etc.) or of polymeric resin preferably charged. When the temperatures of utilization allows it, it is advantageous to use the latter kind of material that offers not only the advantage of being easy to repair but also that does not require, for its setting, heating to a high temperature that is likely to warp the support of the joint which is generally a metallic collar bound to the stator or which constitutes an element of the stator itself.
An abradable joint cannot achieve an absolute air tightness. The unavoidable tolerances of tooling and assembling that cause ovalizations and offsettings, as well as the differences in dilatations that happen when the thermic conditions are not stationary, at the time of variation of the rotation speed for example, result in the fact that there remains a more or less pronounced gap between the internal wall of the joint and the tips of the blades. It has been found that by setting during the tooling, by means of turning, for example, circular grooves into the said internal surface of the joint, the flow of leak is substantially reduced. Indeed, these grooves cause eddies generating additional losses of charge that occur in addition to those due to the throttling. But, this tooling and the preliminary setting will keep a large size machine busy for a relatively long period of time.